The present invention relates to a controlled-type liquid-filled vibration isolator used for supporting a power unit, such as an automotive engine in an anti-vibratory fashion.
Conventionally, as a liquid-filled vibration isolator used in a mount for support not to transmit the vibration of a vibrating body, such as an automotive engine, there has been a proposal of a controlled-type liquid-filled vibration isolator adapted to switch the anti-vibration characteristic depending upon two kinds of vibrations having a different frequency region, such as shake vibration and idle vibration.
For example, Japanese Patent Laid-open No. 173372/1999 proposes a controlled-type liquid-filled vibration isolator having an anti-vibration basic member formed by a metal fitting on a vibration-source side, an outer cylindrical metal fitting on a support side and a rubber elastic member interposed between them, a first diaphragm attached on the outer cylindrical metal fitting oppositely to the anti-vibration basic member and a partition arranged between the diaphragm and the anti-vibration basic member, wherein a main liquid chamber is formed between the partition and the anti-vibration basic member and a first sub liquid chamber is formed to have communication with the main liquid chamber through a first orifice between the partition and the first diaphragm, and further a second sub liquid chamber is provided on a main-chamber side of the partition to have communication with the main liquid chamber through a second orifice and a switch chamber isolated from the second chamber by a second diaphragm to enable switching and admitting atmospheric pressure and negative pressure.
Meanwhile, in the case of the proposed device, the structural members for the partition must be press-fitted and assembled in order while positioning an orifice opening in a liquid. There are problems with complicated assembling, insufficient stability and so on. For this reason, the present applicant has proposed a liquid-filled vibration isolator having a structure the partition is to be temporarily assembled in air to press-fit and assemble in a liquid the temporarily-assembled partition in an inner periphery of a cylindrical metal fitting vulcanization-adhered to the anti-vibration basic member (Japanese Patent Application No. 256996/1999).
In any of the above controlled-type liquid-filled vibration isolators, the main member of the partition has a switch-admission passage communicating from the switch chamber to the outer periphery in order to switch the admission of atmospheric pressure and negative pressure in the switch chamber provided on the main-liquid-chamber side, providing connection switch means, such as a switching valve, of between atmospheric pressure and negative pressure through an admission pipe. The admission pipe is press-fitted in the passage penetrating the cylindrical metal fitting and opened in the outer periphery of the partition main member.
Usually, in air the admission pipe is press-fitted into the passage after the structural parts, such as the partition, including the first and second orifices are press-fitted and assembled in an inner periphery of the cylindrical metal fitting in a liquid.
Consequently, the press-fit pressure of the admission pipe during the assembling acts upon the main member of the partition in a direction of press-fit, or in a constant radial direction. The main member of the partition is relatively displaced by the affection of compression or the like of the seal rubber layer. As a result, the sealability in the outer periphery lowers resulting in a problem that stable liquid filling and assembling is difficult to keep.
In particular, with decrease in the outer peripheral thickness of the main member to which the admission pipe is to be press-fitted, the pressure increases that is received at the opposite portion to the side of press-fitting the admission pipe in the outer peripheral surface thus readily causing deviation due to relative displacement during press-fitting. Consequently, even where the main member of the partition is formed by an integrally-formed part of a metal material, such as aluminum, or a synthetic resin, there is a limitation in decreasing the outer peripheral thickness of the main member. Thus, there is a problem of impossible contribution to weight reduction.
The present invention has been made in view of the foregoing, and structured, in the above controlled-type liquid-filled vibration isolator, to reduce the affection due to pressure-fitting of the admission pipe for switching and admitting atmospheric pressure and negative pressure to a switch chamber thereby obtaining stable liquid filling and assembling and further providing contribution to weight reduction.
The present invention is a controlled-type liquid-filled vibration isolator comprising: an anti-vibration basic member formed by a rubber elastic member; a first metal fitting coupled to one of upper and lower sides of the anti-vibration basic member; a second metal fitting having a cylindrical barrel coupled to the other side of the anti-vibration basic member; a first diaphragm attached in the cylindrical barrel oppositely to the anti-vibration basic member; a partition arranged between the anti-vibration basic member and the first diaphragm; a main liquid chamber formed between the partition and the anti-vibration basic member; a first sub liquid chamber formed between the partition and the first diaphragm; a switch chamber capable of admitting, by switching, atmospheric pressure and negative pressure formed inward at a main liquid chamber side of the partition by a second diaphragm; a second sub liquid chamber isolated from the switch chamber by the second diaphragm; and first and second orifices respectively communicating the main liquid chamber with the first and second sub liquid chambers, and has the following structure in order to achieve the foregoing problem.
The partition has a partition main member having a recess for orifice forming a first orifice at a side of the first sub liquid chamber in an outer periphery and a partition plate member arranged at a side of the main liquid chamber of the partition main member to form the second sub chamber and second orifice, these being fitted on the cylindrical barrel through a seal rubber layer, and further a passage communicating from the switch chamber to the outer periphery being provided in the partition main member and the passage is fitted with an admission pipe for switching between atmospheric pressure and negative pressure penetrating the cylindrical barrel. The partition main member has a seal surface in contact with the seal rubber layer in an inner periphery of the cylindrical barrel, in an outer periphery thereof at around an opening end of the passage in a manner surrounding same, and a pressure-receiving surface broader than the other portion of the outer periphery being provided on an opposite side to the seal surface sandwiching a device axis to enable dispersion of an external force upon press-fitting the admission pipe.
According to the liquid-filled vibration isolator of this structure, each structural part for a partition to be assembled in the interior is press-fitted and assembled in the cylindrical barrel of the second metal fitting, and thereafter the admission pipe for admitting atmospheric pressure and negative pressure to the switch chamber is press-fitted and assembled in the passage provided in the internal partition main member through a hole provided in the cylindrical barrel. On this occasion, because the opposite side to an opening end of the passage to receive the greatest force upon press-fitting the admission pipe is provided with a pressure-receiving surface broader than the other portion, the contact area of that portion with the seal rubber layer on an inner periphery of the cylindrical barrel increases. The external force upon press-fitting the admission pipe can be dispersed by receiving it by this pressure-receiving surface thereby preventing the partition main member from relatively displacing due to compression or the like of the seal rubber layer. This, together with the formation of the seal surface at around the opening end of the passage ready to loosen in a manner surrounding the same, can favorably keep sealability between the partition main member and the seal rubber layer on an inner periphery of the cylindrical barrel, thus securing stable liquid filling and assembling.
It is preferred in the liquid-filled vibration isolator that the recess for orifice provided at a side of the first sub liquid chamber in an outer periphery of the partition main member is formed avoiding the seal surface and pressure-receiving surface thereby forming the seal surface and pressure-receiving surface to possess a surface broader than the other portion. This makes it possible to form the first orifice with a sufficient length and secure a seal surface and pressure-receiving surface broader than the other portion without increasing the thickness of the partition main member so much.
Also, it is preferred that the second sub liquid chamber and the second orifice are respectively formed at an inward and an outer periphery by the partition plate member arranged on a main liquid chamber side of the partition main member, the partition main member having a portion on an outer periphery upper surface of the partition main member corresponding to the second orifice being cutout in an area except for a portion of the seal surface and pressure-receiving surface. This makes it possible to set the second orifice with a great sectional area while securing a broad seal surface and pressure-receiving surface. Also, it is possible to reduce a material used for the partition main member and contribute to weight reduction.
In the liquid-filled vibration isolator, the recess for orifice provided at a side of the first sub liquid chamber in the outer periphery of the partition main member can be bent back inward at a required point to extend in an arcuate form about a device center, to have a length of approximately 1.0 to 1.5 times a circumference.
A partition retaining plate can be fixed by press-fit means at a side of the first sub liquid chamber of the partition main member, an opening of the recess for orifice on a side of the first sub liquid chamber being covered by the partition retaining plate thereby forming the first orifice, and the opening being provided in a position matched to the recess bent back of the partition retaining plate. This makes it easy to fabricate the partition main member. Furthermore, by adjusting the position of the opening within a length range of the bent-back recess, the length of the first orifice can be easily adjusted.